Excavating wheel



April 11, 1967 L. SOVA EXCAVATING WHEEL Filed Oct. 12, 1964 INVENTOR. ofad/s/a 1/- J6 u-a BY United States Patent EXCAVATIN G WHEEL Ladislav Sova, Unicov, Czechoslovakia, assignor to Unicovsk Strojirny, narodni podnik, Unicov, Czechoslo- This invention relates to rotary excavating machines, and particularly to a blade-carrying excavating wheel. In its more specific aspects, the invention is concerned with the discharge of excavated material from the excavating wheel.

Rotary excavating machines are equipped with wheels carrying peripheral blades which are brought into engagement with the material to be excavated while the wheel is being rotated. The blades cut into the material, and the loose pieces of material are then removed from the excavation site. It is common practice to remove the loose material from the immediate working area of the wheel by two basic methods. In one method, the cut material drops from the blades into chambers provided on the Wheel, and is transferred from the chambers by gravity to a conveyor after traveling circumferentially with the wheel over a suitable angle. Gravity transfer of the excavated material is relatively slow, particularly when impeded by friction between the loose material and contacting walls of the excavating machine. The rate of material transfer from the wheel to the conveyor limits the capacity of the excavating machine.

The second method provides for direct transfer of the loose material from the blades to a conveyor and thus avoids friction between the material and the walls of chambers or chutes. The rotary speed of chamberless excavating wheels is limited by the necessity of holding centrifugal forces below the value at which they would overcome the weight of the loose material.

Available materials of construction, power sources, and other design elements would permit operation of excavating wheels at speeds much higher than are possible with the chamber wheels or the chamberless wheels described above, and its has been proposed to provide an excavating wheel with buckets that retain the loose material as it comes from the blades until the buckets reach an emptying position angularly spaced from the cutting position of the blades, and to arrange mechanical devices on the wheel which release the material from the buckets in the emptying position. Stationary shields arranged between the cutting position and the emptying position have heretofore been suggested to avoid premature centrifugal discharge of the loose material, and buckets having openings with movable covers have also been proposed.

While the last-described devices permit rotation of the excavating wheel at higher speeds than were previously available, they are relatively complicated and involve friction between the abrasive excavated material and movable machine elements where small clearances are fairly critical, and wear of these elements limits the useful life of such devices.

It is the object of the invention to overcome the limitations on the operating speed of a rotary excavating machine inherent in the conventional chamber wheels and chamberless wheels while avoiding the shortcomings of the devices heretofore recommended for this purpose.

A more specific object is the provision of an excavating wheel which mainly relies upon centrifugal forces for discharge of the excavated material from buckets on the wheel, yet does not require devices or mechanisms that rely on sealing engagement between the bucket and a wall or cover for preventing premature discharge of the material.

Another object is the provision of an excavating wheel in which friction between the excavated material and the buckets of the wheel during discharge is very low so as not to hamper discharge.

An additional object is the provision of an excavating wheel in which the loose material travels from each blade into a bucket and is discharged from the bucket over a very short path in contact with the wheel structure.

With these and other objects in view, the invention mainly resides in a wheel which is mounted on the support structure of an excavating machine for rotation about an axis. Several blades are mounted on the wheel rim in circumferentially spaced relationship and radially project from the wheel. A pivot adjacent each blade carries a bucket which is thereby enabled to swing in a plane transverse of the axis of wheel rotation. A tension member connects a portion of each bucket spaced from the associated pivot with a portion of the support structure which is intermediate the wheel rim and the axis of rotation.

The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawing the sole figure of which shows an excavating wheel of the invention and as much of the other elements of a rotary excavating machine as is necessary for an understanding of this invention, the view being in elevational section :at right angles to the axis of the excavating Wheel.

The wheel includes two identical disks 5 which are coaxially mounted on respective heavy stub shafts 6, only one disk and the associated shaft being visible in the drawing. The shafts are elements of the non-rotating support structure of the excavating machine, not otherwise shown, which also includes a motor and a power transmission train connecting the motor to the disks for rotating the same on their shafts as indicated by a curved arrow.

The two disks are fixedly connected by four axially elongated cutting blades 4 which are attached to the disk rims at from each other and projects from the wheel in an oblique direction which is radially outward and circumferentially forward relative to the direction of wheel rotation. The cutting blades project obliquely as well as on both sides of the disks 5, enabling the excavating wheel to cut material when the apparatus moves to and fro in the direction of the Wheel axis. The disks 5 are further connected by four pivot pins 7 which are journaled in the Wheel rims immediately adjacent each fixed cutting blade 4. Each pin 7 carries a bucket 1 which extends between the two disks 5 with only suflicient axial clearance to permit free swinging movement of the bucket on its pin 7.

The buckets are made of rigid metal plates. The portions of these plates adjacent the pins 7 are almost flat, whereas the free portions remote from the associated pivot pin are arcuate in radial section and have a radius of curvature much smaller than the radius of the disks 5, the concave face of each bucket facing at least partly in the direction of wheel rotation.

A pin is coaxially arranged in each of the stub shafts 6 and carries a crank arm 3 between the disks 5. The pins 8 are normally secured in the associated shafts 6 against rotation, but may be pivoted through an angle of about 45 in either direction from the illustrated position and may again be fastened to the stub shaft 6 in the adjusted position in a manner not further illustrated.

The free ends of the crank arms 3 are connected by an axially extending rod 9 which is pivotally attached to the arms 3. Respective end portions of four pliable belts 2 are attachedto the rod 9, and the freeend portions of the belts are respectively secured to fasteners on the convex rear faces of the buckets 1, the fasteners being located at the border between the approximately flat and strongly curved portions of each bucket 1.

When the excavating machine is operated to remove layers from a body of soil 11, the machine travels in the direction indicated by a straight arrow while the wheel is being rotated. The pressure of the material being scooped up by the blades 4 and centrifugal forces tend to swing the buckets 1 clockwise, as viewed in the drawing, and the clockwise bucket movement is limited by the belts 2 which are thereby tensioned. The belts are of equal length, but permit swinging motion of the buckets during wheel rotation because of the radial spacing between the rod 9 and the axis of wheel rotation, the rod being arranged approximately diametrically opposite the desired discharge position of the buckets and near the wheel circumference where the blades 4 cut into the sail 1 1.

While the buckets are being filled with loose soil near the rod 9, their relatively flat portions are oriented to be predominantly tangential or circumferential with respect to the axis of rotation so that the centrifugal forces acting on the loose material in the bucket are largely absorbed by the bucket wall, and the material retained in the bucket does not tend to slide along the bucket surface toward the associated blade 4. As the buckets move away from the rod 9, the belts 2 pull them toward a position in which the relatively flat bucket wall approaches a radial orientation so that the centrifugal forces can cause discharge of the excavated material toward a conveyor, not shown, suitably arranged near the discharge position of the buckets. Only a very small component of the centrifugal forces is perpendicular toward the bucket surface in the discharge position, and friction between the bucket contents and the bucket wall during discharge is small.

Wear by the excavated material is limited to the faces of the buckets 1 and of the disks 5 which confine the loose soil during transfer from the working area of the blades 4 to the discharge position of the buckets, and such wear is relatively minor because there is very little relative movement between the soil and the confining walls of the bucket cavity when the contact pressure is high, and very little contact pressure when the relative movement is fast. Neither the disks 5 nor the buckets 1 have critical dimensions which would be rapidly affected by frictional wear.

The belts 2 may be made of material commonly employed in belt conveyors for abrasive material, such as a fabric base encased in rubber, preferably synthetic rubber, and have a long useful life. During the swinging movement of the buckets 1, the belts are gradually wrapped about the convex face portion of the free bucket end and again unwrapped until they extend substantially in a plane between the rod 9 and the fastener 10. The radius of curvature of the convex bucket face is many times greater than the thickness of the belts 2, and the flexural stresses imposed upon the belts during operation of the excavating wheel are minimal. Relative movement between the belts and the associated convex bucket portion is at right angles to the surfaces of both. The belts are thus not subjected to friction by soil particles that may be trapped between belt and bucket.

The angular position of the rod 9' relative to the axis of rotation may be shifted to adapt the wheel to variations in operating conditions such as depth of excavating cut and location of the associated conveyor.

The excavating wheels of the invention may be rotated at any speed that is consistent with the mechanical strength of the materials of construction and with the power available for turning the wheel and for advancing it into the material to be excavated. The rate of material discharge'from thexwheel is always commensurate with the rate of excavation under otherwise similar conditions.

It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention, and that it is'intended to cover all changes and modifications of the example of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.

What is claimed is:

1. In an excavating machine, in combination:

(a) a support;

(b) a wheel arranged for rotation relative to said support about an axis, said wheel having a rim portion spaced from said axis;

(c) a plurality of blades mounted on said rim portion in circ-umferentially spaced relationship, said blades radially :and axially projecting from said wheel;

(d) pivot means on said rim portion adjacent each of said blades;

(e) a bucket mounted on each pivot means for pivoting movement in a plane transverse of said axis; and

(f) a plurality of tension members, each of said tension members having two end portions respectively secured to a portion of said support intermediate said axis and said rim portion and to a portion of a respective bucket spaced from the associated pivot means.

2. In a machine as set forth in claim 1, said portion of said support having an axis substantially parallel to the axisof rotation of said wheel and being adapted to be rotatable about the axis thereof.

3. In a machine as set forth in claim 2, the axis of said portion being normally angularly fixed with respect to said axis of rotation.

4. In a machine as set forth in claim 1, each bucket having a first portion adjacent the associated pivot means and a second portion remote from said pivot means, said second portion having a convex face, and fastening means securing an end portion of the associated tension member to said bucket for movement of the tension member toward and away, from abutting engagement with said convex face when said wheel rotates at a speed suflicient to cause pivoting movement of said bucket under centrifugal forces, the length of said tension member being selected to limit said movement.

5. In a machine as set forth in claim 1, each bucket having a first portion adjacent the associated pivot means and a second portion remote from said pivot means, said portions having respective faces jointly defining a'bucket cavity, the face of said second bucket portion being concavely arcuate, and having a'radius of curvature substantially smaller than the radius of said rim portion.

6. In a machine as set forth in'claim 5, the face of said first bucket portion being substantially flat.

7. In a machine as set forth in claim 1, said tension member being an elongated belt.

References Cited by the Examiner UNITED STATES PATENTS 847,330 3/1907 Grossmith 37190 3,049,823 8/1962 Spalding 37-190 FOREIGN PATENTS 63,349 3 1945 Denmark. 249,075 3/ 1948 Switzerland. 312,084 2/ 1956 Switzerland.

ABRAHAM G. STONE, Primary Examiner.

R. L. HOLLISTER, Assistant Examiner. 

1. IN AN EXCAVATING MACHINE, IN COMBINATION: (A) A SUPPORT; (B) A WHEEL ARRANGED FOR ROTATION RELATIVE TO SAID SUPPORT ABOUT AN AXIS, SAID WHEEL HAVING A RIM PORTION SPACED FROM SAID AXIS; (C) A PLURALITY OF BLADES MOUNTED ON SAID RIM PORTION IN CIRCUMFERENTIALLY SPACED RELATIONSHIP, SAID BLADES RADIALLY AND AXIALLY PROJECTING FROM SAID WHEEL; (D) PIVOT MEANS ON SAID RIM PORTION ADJACENT EACH OF SAID BLADES; (E) A BUCKET MOUNTED ON EACH PIVOT MEANS FOR PIVOTING MOVEMENT IN A PLANE TRANSVERSE OF SAID AXIS; AND (F) A PLURALITY OF TENSION MEMBERS, EACH OF SAID TENSION MEMBERS HAVING TWO END PORTIONS RESPECTIVELY SECURED TO A PORTION OF SAID SUPPORT INTERMEDIATE SAID AXIS AND SAID RIM PORTION AND TO A PORTION OF A RESPECTIVE BUCKET SPACED FROM THE ASSOCIATED PIVOT MEANS. 